Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$144.59	4.375%	$150.9158	$150.92	$150.90	$150.90
Purchase #2	$155.50	6.501%	$165.6091	$165.61	$165.60	$165.60
Purchase #3	$178.57	5.614%	$188.5949	$188.59	$188.60	$188.60
Purchase #4	$199.94	4.681%	$209.2992	$209.30	$209.30	$209.30
Purchase #5	$201.63	11.703%	$225.2268	$225.23	$225.25	$225.20
Purchase #6	$125.82	3.782%	$130.5785	$130.58	$130.60	$130.60
Purchase #7	$11.34	8.118%	$12.2606	$12.26	$12.25	$12.30
7 purchase totals =	$1,017.39		$1,082.4849	$1,082.49	$1,082.50	$1,082.50